Radial compressor stage

ABSTRACT

A radial compressor stage includes an impeller with multiple impeller blades on the rotor side and a diffuser with multiple guide blades on the stator side positioned downstream of the impeller. Between the impeller and the stator an impeller side gap is formed. Flow inlet edges of the guide blades on the stator side lie on a first circle contour such that the flow inlet edges of all guide blades on the stator side have an identical spacing to the flow inlet edges of the respective adjacent guide blades. Flow outlet edges of the guide blades on the stator side lie on a second circle contour such that in at least one first circumferential position the flow outlet edge of the respective guide blade on the stator side has a spacing to the flow outlet edge of at least one adjacent guide blade other than in second circumferential positions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a radial compressor stage for a radial compressor.

2. Description of the Related Art

From DE 195 02 808 C2 the fundamental construction of a radial compressor having at least one radial compressor stage is known. Accordingly, it is disclosed in this prior art that the or each radial compressor stage of a radial compressor comprises an impeller rotating with respect to a stator, wherein the impeller comprises a hub and multiple impeller blades on the rotor side. Each impeller blade of the impeller comprises a flow inlet edge and a flow outlet edge. Between the flow inlet edge and the flow outlet edge of each impeller blade a suction side, a pressure side, and an outer surface facing the stator extends. The outer surface of the respective impeller blade borders the stator and serves for sealing relative to the stator. Such an impeller of a radial compressor, in which the outer surfaces of the impeller blades directly border the stator, does not comprise a shroud and is also called open impeller. The impeller blades are positioned in an impeller flow channel that is bounded by the hub of the impeller and the stator.

Furthermore it is known from DE 195 02 808 C2 that the radial compressor stage comprises a diffuser positioned downstream of the impeller that comprises multiple guide blades on the stator side. Each guide blade of the diffuser has a flow inlet edge and a flow outlet edge. Between the flow inlet edge and the flow outlet edge of each guide blade a suction side and a pressure side extends. The guide blades are positioned in a diffuser flow channel bounded by the stator.

From DE 195 02 802 C2 it is evident that between the impeller and the stator of the radial compressor stage shown there, a so-called impeller side gap is formed, namely between a back side of the impeller and the stator. This impeller side gap is connected to an intermediate flow channel that extends between the impeller flow channel and the diffuser flow channel.

A further radial compressor stage with such an impeller side gap is known from DE 10 2007 019 264 A1.

From EP 2 014 925 A1 a radial compressor stage with a diffuser is known, in which the angular spacing of flow inlet edges of two guide elements arranged adjacent to one another differs from the angular spacing of flow inlet edges of two other guide elements arranged adjacent to one another.

During the operation of a radial compressor, the radial compressor stages are exposed to mechanical excitations and oscillations that can cause damage to the radial compressor stage, in particular to the impeller blades of the impeller of the radial compressor stage. Such mechanical excitations can be based on synchronous excitation mechanisms and on asynchronous excitation mechanisms.

In particular, three-dimensional and unsteady flow phenomena are generated through the interaction of rotating and stationary components. Under certain conditions, pressure fluctuations develop, which have a character rotating in direction of rotation or in a direction that is opposite to the direction of rotation. The number and the rotating speed of these pressure fluctuations are arbitrary.

This phenomenon is the basis of an asynchronous excitation of open impellers in radial compressors. Up to now, no methods are known with the help of which such asynchronous excitations can be specifically counteracted in order to avoid a critical vibration excitation in particular of the impeller blades of the impeller.

SUMMARY OF THE INVENTION

There is a need for a radial compressor stage for a radial compressor, in which the impeller blades of the impeller are exposed to low vibration excitation through such asynchronous excitations.

One embodiment of the present invention is based on creating a radial compressor stage for a radial compressor that fulfils the above requirements and accordingly is exposed to a low vibration excitation in particular through such asynchronous excitations.

According to a first aspect of the invention, this object is solved through a radial compressor stage. Accordingly, the flow inlet edges of the guide blades of the diffuser on the stator side lie on a first circle contour namely in such a manner that the flow inlet edges of all guide blades on the stator side have an identical spacing from the flow inlet edges of the respective adjacent guide blades. The flow outlet edges of the guide blades of the diffuser on the stator side lie on a second circle contour, namely in such a manner that in at least one first circumferential position the flow outlet edge of the respective guide blade on the stator side has a spacing from the flow outlet edge of at least one adjacent guide blade other than in second circumferential positions.

According to one embodiment of the invention, a radial compressor stage includes, at least one guide blade of the diffuser on the stator side that has a curvature which deviates from the other guide blades on the stator side.

According to a one embodiment of the invention a radial compressor stage wherein, in at least one first circumferential position, a diffuser flow channel section formed between adjacent guide blades of the diffuser on the stator side has a flow cross section which deviates from the diffuser flow channel sections formed on second circumferential positions.

With each of the above aspects according to the invention, asynchronous excitations of open impellers in radial compressors can be easily and reliably counteracted, as a result of which the vibration excitation in particular for the impeller blades of the impeller of the radial compressor stage can be reduced.

Here, the above aspects according to the invention can be employed on a radial compressor stage either alone or preferably combined with multiple such aspects according to the invention.

The above aspects according to the invention altogether relate to measures for the design configuration of the diffuser.

Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred further developments of the invention are obtained from the subclaims and the following description. Exemplary embodiments of the invention are explained in more detail with the help of the drawing without being restricted to this. It shows:

FIG. 1: is a meridional section through a radial compressor stage according to the invention according to a first aspect of the invention;

FIG. 2: is an axial section through the radial compressor stage of FIG. 1;

FIG. 3: is an axial section through a radial compressor stage according to a second aspect of the invention; and

FIG. 4: is a meridional section through a radial compressor stage according to the invention according to a third aspect of the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The present invention relates to a radial compressor with at least one radial compressor stage.

FIG. 1 shows a detail of a radial compressor stage according to the invention in meridional section according to a first aspect of the invention, and FIG. 2 shows an axial section through the radial compressor stage of FIG. 1.

The radial compressor stage of FIG. 1 comprises an impeller 10 with multiple impeller blades 11 on the rotor side. The impeller 10 rotates relative to the stator 12. The stator 12 can be a housing or a stator ring or the like. The impeller blades 11 are positioned in an impeller flow channel 13 bounded by a hub contour 14 on the rotor side and a stator contour 15. Each impeller blade 12 comprises a flow inlet edge 16 and a flow outlet edge 17. Between the flow inlet edge 16 and the flow outlet edge 17 of each impeller blade 11 a pressure side, a suction side and radially outside on the impeller blade 11 an outer surface 18 of the respective impeller blade 11 facing the stator 12 extends. The outer surface 18 of the impeller blade 11 borders the stator 12 and serves for sealing relative to the stator 12. Such an impeller 10, in the case of which the outer surfaces 18 of the impeller blades 11 indirectly border the stator 12 does not have a shroud and is also called an open impeller.

According to FIG. 1, a diffuser 19 on the stator side is positioned downstream of the impeller 10. The diffuser 19 comprises multiple guide blades 20 on the stator side. The guide blades 20 of the diffuser 19 on the stator side are positioned in a diffuser flow channel 21 bounded by the stator 12. Each of the guide blades 20 of the diffuser 19 on the stator side comprises a flow inlet edge 22 and a flow outlet edge 23. Between the flow inlet edge 22 and the flow outlet edge 23 of the respective guide blade 20 on the stator side a suction side 24 and a pressure side 25 of the respective guide blade extends.

Between the impeller flow channel 13, in which the impeller blades 11 of the impeller 10 on the rotor side are positioned, and the diffuser flow channel 21, in which the guide blades 20 of the diffuser 19 on the stator side are positioned, an intermediate flow channel 26 extends, via which medium compressed in the radial compressor stage starting out from the impeller 10 can flow in the direction of the diffuser 16. According to FIG. 1, a impeller side gap 28 is formed between a back side 27 of the impeller 10 and the stator 12, wherein this impeller side gap 28 according to FIG. 1 is coupled to the intermediate flow channel 26 via a gap 34.

The invention relates to such details of a radial compressor stage with the help of which the danger of unsteady flow phenomena, which can lead to asynchronous excitation of the open impellers, can be reduced.

According to a first aspect of the invention, which is described in the following making reference to FIGS. 1 and 2, all flow inlet edges 22 of all guide blades 20 of the diffuser 19 on the stator side lie on a first circle contour 29.

Here, the flow inlet edges 22 of the guide blades 20 of the diffuser 19 on the stator side lie on the first circle contour 29 in such a manner that the flow inlet edges 22 of all guide blades 20 on the stator side have an identical spacing from the flow inlet edges 22 of the respective adjacent guide blades 20. The flow inlet edges 22 of the guide blades 20 of the diffuser 19 located seen in circumferential direction of the diffuser flow channel 21 next to one another are accordingly evenly distributed seen in circumferential direction, so that accordingly all flow inlet edges 22, which lie on the first circle contour 29, have identical circumferential spacings to adjacent flow inlet edges 22.

According to the first advantageous further development of the first aspect and/or second aspect of the invention it is provided, furthermore, that the flow outlet edges 23 of the guide blades 20 of the diffuser 19 on the stator side lie on a second circle contour 30.

The flow outlet edges 23 of the guide blades 20 of the diffuser 19 on the stator side lie on the second circle contour 30 such that in at least one first circumferential position of the diffuser flow channel 21 the flow outlet edge 23 of the respective guide blade 20 on the stator side positioned there has a spacing from the flow outlet edge of at least one adjacent guide blade 20 other than in second circumferential positions of the diffuser flow channel 21.

In the region of the flow outlet edges 23, no equal distribution of the flow outlet edges 23 is provided seen in circumferential direction of the diffuser flow channel 21. In contrast the equal distribution of the flow outlet edges 23, which all lie on the second circle contour 30, is preferentially cancelled in the first circumferential positions in order to thereby reduce the risk of unsteady flow phenomena, which can lead to an asynchronous excitation of the open impellers.

According to the first advantageous further development of the first aspect and/or second aspect of the invention it is possible in a first extreme case that the corresponding flow outlet edge 23 in a single circumferential position of the diffuser flow channel 21 has another spacing from the respective adjacent flow outlet edges 23, that by contrast in the other circumferential positions the flow outlet edges 23 with respect to their circumferential positions are equally distributed.

It is likewise possible according to the first advantageous further development of the first aspect and/or second aspect of the invention in a second extreme case that in all circumferential positions of the diffuser flow channel 21 the flow outlet edges 23 have different spacings in each case from the respective adjacent flow outlet edges 23.

In the second circumferential positions of the diffuser flow channel 21, the respective guide blades 20 of the diffuser 19 on the stator side preferentially all have identical, second stepping angles.

The guide blades 20 on the stator side positioned in the or each first circumferential position by contrast preferentially have a first stepping angle, which deviates from the second stepping angle, in particular by plus minus ±10°, preferably by plus minus ±7°, particularly preferably by ±5°, most preferably by ±3°.

According to the first advantageous further development of the first aspect and/or second aspect of the invention it is accordingly proposed for reducing the danger of unsteady flow phenomena, which can lead to an asynchronous excitation of the open impellers, to reposition the flow outlet edges 23 of selected guide blades 20 of the diffuser 19 on the stator side in circumferential direction, preferentially subject to cancelling or interrupting the flow outlet edges 23 which seen in circumferential direction of the diffuser flow channel 21 are otherwise equally distributed.

In an extreme case, the flow outlet edges 23 of all guide blades 20 of the diffuser 19 on the stator side can have different spacings from the respective adjacent flow outlet edges 23.

As is evident in FIG. 2, a flow outlet edge 23″ (see dashed line course of the in FIG. 2 right guide blade) in the direction of the pressure side 25 of the respective adjacent guide blade 20 or a flow outlet edge 23′ (see dashed line course of the in FIG. 5 left guide blade) be relocated in circumferential direction in the direction of the suction side 24 of the respective adjacent guide blade 20 namely in such a manner that all flow outlet edges 23 as before still lie on the second circle contour.

This corresponds to a change of the stepping angle of the guide blades 20 of the diffuser 19 on the stator side in selected circumferential positions. In selected second circumferential positions of the diffuser 19, the respective guide blades 20 on the stator side have deviating stepping angles.

Those selected guide blades 20, which compared with the remaining guide blades 20 on the stator side, have a different stepping angle are characterized in that their stepping angle deviates in particular by ±10°, particularly preferably by ±5° from the stepping angles of the remaining guide blades 20 of the diffuser 19.

Through the above measures of the first advantageous further development of the first aspect and/or second aspect of the invention, a slightly higher or a slightly lower loading can be imposed on the guide blades 20 of the diffuser 19 in defined circumferential positions at uneven circumferential spacings. The danger of unsteady flow phenomena which can lead to an asynchronous excitation of the open impellers can thereby be further reduced.

According to a second aspect of the invention shown in FIG. 3, it is proposed for reducing the risk of unsteady flow phenomena, which can lead to asynchronous excitation of the open impellers, that both the flow inlet edges 22 of the guide blades 20 of the diffuser 19 on the stator side positioned on the first circle contour 29 as well as the flow outlet edges 23 of the guide blades 20 of the diffuser 19 on the stator side positioned on the second circle contour 30 are equally distributed in circumferential direction, i.e. in each case have identical circumferential spacings.

However, according to the second aspect of the invention, at least one guide blade 20 of the diffuser 19 on the stator side has a deviating curvature between the flow inlet edge 22 and the flow outlet edge 23, namely a suction side 24′ and a pressure side 25′ with a curvature which deviates relative to the other guide blades 20. This is shown in FIG. 3 by the dashed course for the middle guide blade 20.

According to the second aspect of the invention it is possible in a first extreme case that exclusively a single guide blade 20 of the diffuser 19 on the stator side has a deviating curvature, that by contrast all other guide blades 20 of the diffuser 19 on the stator side have identical curvatures.

It is likewise possible in a second extreme case according to the second aspect of the invention that all guide blades 20 of the diffuser 19 on the stator side have curvatures that deviate from one another.

It is preferred to employ the first aspect of the invention and the second aspect of the invention combined with one another for reducing the risk of unsteady flow phenomena, which can lead to asynchronous excitation of the open impellers, on the radial compressor stage.

A third aspect of the present invention is discussed in the following making reference to FIG. 4.

According to the third aspect of the invention, it is proposed for reducing the risk of unsteady flow phenomena that can lead to asynchronous excitation of the open impellers, to change a diffuser flow channel section 33 formed between adjacent guide blades 20 of the diffuser 19 on the stator side in at least one first circumferential position of the diffuser flow channel 21 in such a manner that the same has a deviating flow cross section compared with the diffuser flow channel sections formed in second circumferential positions.

Accordingly it is evident from FIG. 4 that in a first circumferential position of the diffuser 19 between adjacent guide blades 20 on the stator side the respective diffuser flow channel section 33 has a reduced flow cross section, namely because of the fact that the side walls 31, 32 on the stator side bounding the respective diffuser flow channel section 33, are curved towards the inside subject to reducing the flow cross section of the respective diffuser channel section 33. It is pointed out that merely one of these side walls 31, 32 bounding the respective diffuser flow channel 33 can be curved into the respective diffuser flow channel 33. It is likewise possible, in selected circumferential positions, to expand the respective diffuser flow channel section with respect to its flow cross section, wherein at least one of these side walls 31, 32 is then curved towards the outside into the stator 12.

According to the third aspect it is possible in a first extreme case that exclusively in a single circumferential position of the diffuser flow channel 21 the corresponding diffuser flow channel section 33 has a deviating flow cross section, that by contrast all other diffuser flow channel sections 33 have identical flow cross sections.

It is likewise possible according to the third aspect of the invention in a second extreme case that in all circumferential positions of the diffuser flow channel 21 the diffuser flow channel sections 33 each have different flow cross sections.

The measures of the third aspect can be employed combined with the measures of the first aspect and/or the measures of the second aspect. Preferably, the measures of the third aspect are employed on a radial compressor stage combined with the measures of the first aspect and with the measures of the second aspect.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. 

What is claimed is:
 1. A radial compressor stage comprising: a stator; a rotor; an impeller having a plurality of impeller blades on the rotor side rotating relative to a stator; a diffuser having a plurality of guide blades on a stator side positioned in a flow direction downstream of the impeller; and an impeller side gap formed between the impeller and the stator, wherein flow inlet edges of the plurality of guide blades lie on a first circle contour such that the flow inlet edges of the plurality of guide blades have a substantially identical spacing to the flow inlet edges of a respective adjacent guide blades; and wherein flow outlet edges of the plurality of guide blades lie on a second circle contour such that, in at least one first circumferential position, a respective flow outlet edge of a respective guide blade on the stator side has a spacing to the flow outlet edge of at least one adjacent guide blade other than in second circumferential positions.
 2. The radial compressor stage according to claim 1, wherein in the second circumferential positions the respective guide blades all have identical second stepping angles; and in first circumferential position the respective guide blades on the stator side have a first stepping angle that deviates from the second stepping angle.
 3. The radial compressor stage according to claim 2, wherein the first stepping angle deviates from the second stepping angle by ±10°.
 4. A radial compressor stage, comprising: a stator; an impeller having a plurality of impeller blades on a rotor side rotating relative to the stator; a diffuser with a plurality of guide blades on a stator side positioned in flow direction downstream of the impeller; an impeller side gap formed between the impeller and the stator, wherein at least one guide blade has a curvature that deviates from the other guide blades on the stator side.
 5. A radial compressor stage, comprising: a stator; an impeller with a plurality of impeller blades on a rotor side that rotates relative to the stator; a diffuser with a plurality of guide blades on the stator side positioned in flow direction downstream of the impeller; an impeller side gap formed between the impeller and the stator; and a diffuser flow channel section formed between adjacent guide blades on the stator side in at least one first circumferential position has a flow cross section deviating from diffuser flow channel sections formed in second circumferential positions.
 6. The radial compressor stage according to claim 5, wherein relative to the second circumferential positions in the at least one first circumferential position between the adjacent guide blades on the stator side at least one side wall bounding the diffuser flow channel section subject to reducing the flow cross section is curved towards an inside into the diffuser flow channel section and/or subject to enlarging the flow cross section towards an outside into the stator.
 7. The radial compressor stage according to claim 2, wherein the first stepping angle deviates from the second stepping angle by ±7°.
 8. The radial compressor stage according to claim 2, wherein the first stepping angle deviates from the second stepping angle by ±5°. 